What flag is that? Address sanitizer has a 2x performance hit so presumably not that?

-fbounds-safety [1]

Based on their slides [2]. I was wrongly informed one does need to do some light annotation in function signatures and struct definitions for anything ABI relevant. Based on their slides:

Ptrdist and Olden benchmark suites

- LOC changes: 2.7% (0.2% used unsafe constructs) Much lower than prior approaches

- Compile-time overhead: 11%

- Code-size (text section) overhead: 9.1% (ranged -1.4% to 38%)

- Run-time overhead: 5.1% (ranged -1% to 29%)

Measurement on iOS

- 0-8% binary size increase per project

- No measurable performance or power impact on boot, app launch

- Minor overall performance impact on audio decoding/encoding (1%)

[1] https://clang.llvm.org/docs/BoundsSafety.html

[2] https://llvm.org/devmtg/2023-05/slides/TechnicalTalks-May11/...